The present application is a competing renewal of a U19 grant that was awarded in 2003. The stated goals of the original application were threefold: (i) To study the human immune response to a vaccine in its entirety; starting from the innate responses, to the peak effector T and B cell responses, to the development and maintenance of immunologic memory, (ii) To understand how a successful vaccine works, and to use this knowledge for designing strategies for enhancing vaccine efficacy, (iii) To understand the cellular basis of immune senescence and develop strategies for improving responses of the elderly to vaccination. A major emphasis of this proposal was to use genomics to define molecular signatures of a successful vaccine, and to use this knowledge to develop new vaccines against emerging infections. To achieve these goals, we studied one of the most effective human vaccines ever developed, the yellow fever vaccine-17D (YFV-17D) as a model. Our efforts resulted in several important advances, including the elucidation of: (i) the dynamics of antigen-specific T cell responses in humans vaccinated with YFV-17D and smallpox, (ii) innate immune mechamisms by which YFV-17D acts to launch a broad and robust T cell immunity, (iii) genomic signatures capable of predicting the T cell immunogenicity of YFV-17D in humans and (iv) identification of potential molecular defects that underlie the sub-optimal response of aged T cells to vaccination. In this renewal application, we aim to follow up on these exciting observations and to determine the extent to which such responses are unique to YFV-17D relative to other vaccines or viruses. This overall goal will be achieved in three Research Projects: 1. Immune Memory (Ahmed/Boss), 2. Innate Immunity (Pulendran/Rice), 3. Immune Senescence (Goronzy), and a Technology Development Project on Human Monoclonal Antibodies (Wilson/Lanzavecchia). This overall research effort will be supported by an Administrative Core (Ahmed/Ansari), a Clinical Research Core (Mulligan/Chokephaibulkit/Yu) and a Genomics & Computational Biology Core (Haining/Lee). In addition, there will be a program for education of scientists aspiring to do human immunology research, and a mechanism for funding pilot projects in human immunology. RELEVANCE: Vaccination is the most effective means of preventing infectious disease. Despite the success of many vaccines, there is presently little knowledge of the immunological mechanisms that mediate their efficacy. Such information will be critical in the design of future vaccines against old and new infectious diseases. In the present proposal, we aim to understand the immune mechamisms by which a successful vaccine induces long-term protective immunity. PROJECT 1: [IMMUNE MEMORY (Ahmed, R)] PROJECT 1 DESCRIPTION (provided by applicant): Our goal is to understand how a successful vaccine induces long-term immunological memory and protective immunity in humans. To achieve this goal we have initiated a detailed cellular and molecular characterization of human immune responses induced by the yellow fever virus (YFV-17D) vaccine. This is one of our most efficacious vaccines and induces long-term immunity that lasts for decades. Also, since YFV-17D is a live attenuated vaccine and most of the US population is not exposed to YFV-, this provides a unique opportunity to analyze antiviral responses in humans during the course of a primary infection and then to monitor the generation and maintenance of immune memory after resolution of the infection. One of the potential benefits of understanding how a successful vaccine induces long-term protective immunity is that this knowledge can be applied to improving other less effective vaccines and, more importantly, to develop new vaccines against emerging diseases. During the previous cycle of funding we have made substantial progress in characterizing human memory T and B cell responses not only to YFV but also after immunization with small pox and influenza vaccines. In this renewal application we will focus our studies on CD8 T cells and examine the mechanisms that regulate human effector and memory CD8 T cell differentiation. The following specific aims are proposed to achieve our goals: 1) To identify transcription factors that regulate naive to effector CD8 T cell differentiation. 2) To analyze the in vivo turnover of human YFV specific CD8 T cells and to examine their homing potential. 3) To define the genomic and epigenetic changes that occur during human memory CD8 T cell differentiation. These studies will provide the first view of the transcriptional changes that occur following CD8 T cell differentiation in humans and will provide unique markers that will enable identification, isolation, and characterization of the differentiated cell subsets. Examination of the epigenetic DMA methylation marks during the progression of the T cell response, as well as between CD8 T cells responding to acute versus chronic viral infections will provide a potential mechanistic view of how memory CD8 T cell differentiation is globally regulated. RELEVANCE: YFV-17D is an ideal model to study memory T cell generation in the context of an acute viral infection. The underlying importance of this study is that the longitudinal analysis of YFV specific CD8 T cells in vaccinees, offers a unique opportunity to track differentiation of highly functional and long-lived human memory CD8 T cells and generate a signature that may be a benchmark for other vaccines.